It seems that something has been broken in Juce not some long ago regarding the behavior of findColour with inheriting.
Given this hierarchy
A --> B --> C
B has a custom LnF
if in C I call findColour with inheriting but this color is not defined in the component hierarchy but only in the custom B LnF, Juce doesn’t find it.
When inheriting is on, the fallback on the LnF is only on the top most component if the color is not defined in any of the component.
It used to check on the component and custom LnF at each level then get back from one level in the hierarchy which looks like to be a better behaviour imho.